Understanding Arguments: Definition, Validity, and Soundness - Prof. Mark A. Moffett, Study notes of Introduction to Philosophy

Download Understanding Arguments: Definition, Validity, and Soundness - Prof. Mark A. Moffett and more Study notes Introduction to Philosophy in PDF only on Docsity! Introduction to Logic: Argumentation, Validity & Soundness It seems like people are arguing all the time. But these arguments rarely involve arguments (i.e., argumentation) and when they do they are rarely good arguments. So I claim. There are two claims above that we want to look at more carefully. The first and less interesting claim is that people can disagree without giving arguments. The second is that arguments can be evaluated as better or worse. Let’s start with the first point. Consider the following skit from Monty Python: http://www.youtube.com/watch?v=teMlv3ripSM Now there is obviously a sense of “argument” in which the two characters in this skit are having an argument. They are, after all, having a disagreement. But Eric Idle’s character clearly has something more in mind. But what more could be involved? As John Cleese says, “Look if I argue with you, I have take up a contrary position.” And this is right. It does seem like a necessary condition for having an argument (of any sort) that the participants take opposing views. But for the sort of argument that is wanted, this is not a sufficient condition. For merely taking up a contrary position is consistent with the disagreement being merely contradiction: the “automatic gainsaying of anything the other person says.” Idle’s character doesn’t want mere contradiction, but rational argumentation. “An argument is not the same as contradiction. An argument is a collective series of statements to establish a definite proposition.” Here we have a pretty good definition of the logician’s use of the term “argument”. Here is a first pass at the definition: Def. 1a. An argument is any set of statements one of which, the conclusion, is supposed to be supported by the remaining statements, the premises. The essential point here is that when one gives an argument, one is giving (or, at least, attempting to give) the other person a reason to believe the conclusion; that is what the premises are supposed to be doing. But we still haven’t gotten to the bottom of the issue. Consider the following situation: suppose that I tell you that unless you accept the claim that I am the greatest philosopher of all time, I will fail you for this class. Obviously, there is some sense in which I have given you a reason to believe that I am the greatest philosopher of all time. This is not what is intended. What I have given you is a practical or prudential reason to believe, specifically, a reason to believe grounded in your self-interest. What we intended, however, was that an argument provide an epistemic or truth-conducive reason to believe. That is, the premises of the argument are supposed to give us a reason to think that the conclusion is true. (This makes sense. After all, to believe something is to believe that it is true. We will talk more about this issue later in the semester.) So we will want to modify our definition of an argument in order to capture this point: Def. 1b. An argument is any set of statements one of which, the conclusion, is supposed to be epistemically supported by the remaining statements, the premises. This is the definition I want you to know. This brings us to the second point concerning the relative merits of an argument. Just as in the case of architecture (from which the “support” metaphor is borrowed), the epistemic support provided by the premises can be better or worse. To see this, consider an egregious sort of ad hominem argument: http://www.youtube.com/watch?v=V5UJOvVoPcw. Here Dan Akroyd offers an argument to the effect that Michelle is not deserving of any further financial support from the Actor Lee Marvin. While some of his supporting claims may be relevant, most are not. If we think of Akroyd’s tirade as a number of distinct arguments, we can put at least one of those arguments as follows: 1. The defender of Michelle’s right to the money (namely, Jane Curtain) is “an ignorant slut” who “hops from bed to bed with the frequency of a ham radio.” 2. Michelle herself is a “screeching, squealing, rapacious swamp sow.” ______ 3. Therefore, Michelle is not deserving of the any financial support from Marvin The problem here seems to be that, while the premises are supposed to be epistemically supporting of the conclusion, they don’t in fact make the conclusion any more probable. And this suggests that the right way to think about the epistemic goodness of an argument is in terms of epistemic strength. There have traditionally have been two important (and related) ways of thinking about the relation of epistemic strength. One answer, the answer given in deductive logic, says that the premises support the conclusion if, given the truth of the premises, the conclusion must also be true. That is, if there is no way for the premises to be true and the conclusion to be false. The second answer, the one given in inductive logic, says that the premises support the conclusion if, given the truth of the premises, the truth of conclusion is highly probable (but not necessary). In this course we are going to focus primarily on deductive logic, and hence, the first answer. It will be convenient to introduce a simple term for arguments that provide this kind of support for their premises. Def. 2. An argument is valid if and only if the conclusion must be true, given the truth of the premises. It is extremely important to note that the above definition does not say that the premises of the argument are true. In evaluating the validity of an argument we do not concern ourselves with the truth or falsity of the premises. Rather we assume that the premises are true and try to determine whether, given this fact, the conclusion must be true as well. Of course, valid arguments with false or highly controversial premises are of little real value. What we strive for, rather, are arguments with true and relatively uncontroversial premises. Def. 3. An argument is sound if and only if the argument is valid and, in addition, all of its premises are true. When people argue they disagree over something. Moreover, when someone gives an argument they intend to resolve the disagreement one way or the other. Consequently, it does you no good to give an argument containing a premise that is at least as controversial as the claim you are trying to establish. Rather, when you give an argument, your premises should be “common ground” between you and your opponent. That is, when you give an argument, your premises should all be claims upon which you and your opponent agree. Therefore, you should strive to give arguments that are sound and that your opponent agrees to be sound. The Epistemic Regress Problem Call a set of propositions R a conditional reason for believing that p iff R logically supports p. R logically supports p iff there is a (deductively or inductively) valid argument in which the propositions in R are taken as the premises and p is taken as the conclusion.